In recent years, remarkable development of communication networks allows real-time, two-way communications using video phones or the like. The video phone comprises image sensing means for converting an object image into an electrical image signal, and display means for converting the electrical image signal into an optical signal, and displaying that optical signal. The user of the video phone talks while observing the partner's face displayed on the screen of the display means. At the same time, the image of the user's face is sensed and is converted into an electrical signal by the image sensing means, and the electrical signal is sent to the partner side. However, in a conventional device such as a video phone or the like, which is used in two-way communications, the image sensing means is provided in the neighborhood of the display means or as another independent device, and obliquely senses a recipient who observes the display means. For this reason, the partner's face displayed on the display means gazes another place, thus feeling awkward if they talk with each other, and feeling odd compared to a face-to-face conversation. Also, the image sensing device and display device must be independently manufactured and assembled as independent devices, resulting in high manufacturing cost.
To solve these problems, Japanese Patent Laid-Open No. 10-70713 discloses an arrangement which comprises the image sensing means within a display area of the display means. FIGS. 33, 34, and 35 show this prior art: FIG. 33 is an overall perspective view, FIG. 34 is an enlarged sectional view taken along a line A-A′ in FIG. 33; and FIG. 35 shows the image sensing principle of an object. As shown in FIGS. 33 and 34, a transmissive image sensing device integrated display device comprises a display device 1 and transmissive image sensing device 2. The display device 1 is a transmissive liquid crystal display device, and is illuminated with illumination light 5 from behind. The transmissive image sensing device 2 comprises windows 3 which are laid out in a matrix pattern, and microlenses 4 arranged at the intersections of the windows. A video on the display device 1 illuminated with the illumination light 5 is observed via the windows 3 of the transmissive image sensing device 2. The microlenses 4, photodiodes 26, and the like of the transmissive image sensing device are provided on a TFT 10 of the display device 1. Therefore, both image sensing and display functions can be achieved. One microlens 4 and photodiode 26 obtain one image sensing signal.
The image sensing principle of an object by such multi-eye image sensing element will be described below using FIG. 35. FIG. 35 is a vertical sectional view of the transmissive image sensing device 2. The photodiodes 26 are arranged at given intervals on a transparent glass substrate 21 to form a photodiode array 38, and each individual photodiode 26 is covered by a light-shielding layer 30, which has a pinhole 31. A microlens array 35, which is formed by the microlenses 4 corresponding to the individual photodiodes 26, is arranged in front of the photodiode array 38. An object 39 is located in front of the microlens array 35, and external light beams 37 from the object 39 enter the individual photodiodes 26, as shown in FIG. 35. Therefore, each photodiode 26 receives only light 37 in a specific direction that connects the pinhole 31 and the optical center of the microlens 4. If all the external light beams 37 transmitted through the microlens array 35 are parallel to each other, the object 39 located in front of the transmissive image sensing device 2 is sensed to have a size as large as the image sensing device 2.
With this arrangement, an image sensing operation can be made while observing the display means, and the line of sight of the user can match that of the partner displayed on the display means. Since the low-profile image sensing means is provided on the front surface of the display means, the overall device can be prevented from being bulky.
However, the aforementioned prior art suffers the following problems.
(1) The number of pixels of a sensed image is nearly equal to that of the display device, and cannot be increased beyond the number of display pixels.
(2) Since the photodiodes with poor manufacturing yield are formed to have a large substrate size like the display device, the number of photodiodes that can be formed per substrate is small, resulting in high cost.
(3) Photoelectric converters that form the windows are discretely arranged, thus generating moiré stripes.